HPLC Determination of Preservatives in Cosmetics

HPLC was applied to the determination of 7 preservatives, including 6 nipagin esters and benzoic acid, in cosmetics. The sample was ultrasonically extracted with methanol and separated with a mixture of acetonitrile-methanol-NaH2PO4 (15+35+50) as mobile phase on ZORBAX Extend XDB-C18 column (250 mm×4.6 mm, 10 μm). The contents of 7 preservatives were determined at the wavelength 254 nm with DAD. Linear relationships between values of peak area and mass concentration of 7 preservatives were kept in the definite ranges, with their detection limits (3S/N) in the range of 0.4-2.5 mg·L-1. Recovery and precision were tested by adding 7 preservatives standard solution to cosmetic samples of known preservative concentrations at 3 concentration levels, values of recovery found were in the range of 87.5%-98.5%, and values of RSD′s (n=6) found were in the range of 0.41%-2.6%.